1. Field of the Invention
The present invention relates in general to an ink-jet recording apparatus including a recording head which is moved in a predetermined direction for performing recording of images, characters and the like on a recording medium by ejecting inks having mutually different colors from corresponding nozzles. The present invention also relates to a method of cleaning the recording head of the ink-jet recording apparatus.
2. Discussion of Related Art
As an ink-jet recording apparatus which performs recording of images, characters and the like on a recording medium by ejecting inks based on input signals, there is conventionally known one which introduces the inks into the actuator of a recording head and ejects the inks pressurized by utilizing deflection or flexure of piezoelectric elements, electrostrictive elements and so on caused based on the input signals or utilizing local or partial boiling of the inks by heat-generating elements.
FIG. 13 schematically shows a recording head 90 of a conventional ink-jet recording apparatus. The recording head 90 has a plurality of nozzles 91 which are arranged in rows such that ink ejection openings thereof are open in the lower surface of the recording head 90. Each nozzle 91 is defined by side walls formed of a piezoelectric material, and ink droplets are ejected from each ink ejection opening owing to deformation of the side walls formed of the piezoelectric material. To each of the plurality of nozzles 91, there is supplied a corresponding one of inks such as a cyan ink, a yellow ink, a magenta ink, and a black ink from a corresponding one of manifolds 92 which correspond to the respective inks. Each of the manifolds 92 includes a manifold chamber 93 communicating with the corresponding nozzles 91 and an ink supply path 95 through which the corresponding one of the inks is supplied from a corresponding one of buffer tanks 94 to the manifold chamber 93. The ink supplied from a corresponding one of ink tanks not shown is stored in the buffer tank 94 and flowed from the buffer tank 94 to the corresponding nozzles 91 via the manifold 92.
In general, the ink-jet recording apparatus is subjected to a recording operation in factories prior to shipment thereof for the purpose of confirming or checking ink ejecting performance of the apparatus. In the recording operation, the ink tanks are actually installed on the apparatus for supplying the inks therefrom to the recording head 90 to perform the recording operation of recording test patterns, for instance. For shipment of the apparatus after the checking of the recording operation, the ink tanks are removed from tubes for supplying the inks from the ink tanks to the recording head 90, and the openings of the ink tanks and the tubes are respectively sealed by caps or the like. Further, there is attached a cap 96 to the recording head 90 for preventing contamination due to leakage of the inks and drying of the inks in the nozzles 91 during transportation, storage, etc., of the apparatus. The cap 96 is for removing air bubbles and foreign substances from the recording head 90. As shown in FIG. 13, the cap 96 is arranged to cover the ink ejection openings of all nozzles 91 and is connected to a suction pump not shown. With the ink ejection openings of the nozzles 91 covered with the cap 96, the inside of the cap 96 is subjected to a negative pressure, whereby the inks are sucked from the nozzles 91. This ink sucking action is generally called purging that is performed, after the recording head 90 has not been used for a long period of time, as a means for recovering the recording head 90 to a state in which the air bubbles and the foreign substances are not present in the same 90. In this connection, during transportation and storage of the ink-jet recording apparatus, the cap 96 covers the ink ejection openings of the nozzles 91 without performing the ink sucking action.
After shipment of the ink-jet recording apparatus in the state described above, the inks may leak out of the ink ejection openings of the nozzles 91 of the recording head 90 influenced by changes in the temperature and atmospheric pressure, vibration, etc., in the transportation or storage period of the apparatus before a user who has purchased the apparatus initially uses the apparatus. For instance, when the ink tanks are removed from the tubes and the caps are attached to respective ends of the tubes after checking of the ink ejecting performance as described above, the air tends to enter the tubes from the respective ends thereof and stay therein. In the meantime, because valves provided in ink passages from the ends of the tubes to the recording head 90 and a valve of the suction pump connected to the cap 96 are kept open, the inks may leak from the nozzles 91 of the recording head 90 and be drawn into the same 91 when the volume of the staying air varies due to changes in the temperature and atmospheric pressure. The inks which leak from the nozzles 91 gather or collect around the ink ejection openings of the nozzles 91 and mix with one another in the vicinity of the ink ejection openings of the adjacent nozzles 91, so that the mixed ink I enters insides of the nozzles 91 from the ink ejection openings thereof due to the change in the volume of the staying air, the surface tension, etc. Consequently, the insides of the nozzles 91, the manifolds 92, and the buffer tanks 94 may be contaminated with the mixed ink I.
In a case where the recording head 90 performs the recording operation with the nozzles 91 and so on contaminated with the mixed ink I, the mixed ink I is ejected from the nozzles 91 on a recording sheet, so that the recording operation is performed with the inks whose colors are different from original ones. To prevent this, JP-A-59-209877, for instance, discloses the following technique: The above-mentioned ink sucking action called purging by the cap 96 is performed for sucking the mixed ink I from the nozzles 91 and drawing new fresh inks from the ink tanks. Further, the mixed ink I is removed from the nozzles 91 and the manifolds 92 by so-called flushing, i.e., ejecting the inks from the nozzles 91 toward a waste-ink tray.